Buggy code:
public final class ItemTable { private static final ItemTable INSTANCE = new ItemTable ( ) ; public static ItemTable instance ( ) { } private ItemTable ( ) { } private final Map < Integer , ItemType > idToType = new HashMap < > ( 512 ) ; private int nextBlockId ; private int nextItemId ; private void registerBuiltins ( ) { reg ( NOTE_BLOCK , new BlockNote ( ) ) ; reg ( MOB_SPAWNER , new BlockMobSpawner ( ) ) ; reg ( MONSTER_EGGS , new BlockMonsterEggs ( ) ) ; reg ( DRAGON_EGG , new BlockFalling ( Material . DRAGON_EGG ) ) ; reg ( SIGN_POST , new BlockSign ( ) ) ; reg ( WALL_SIGN , new BlockSign ( ) ) ; reg ( WORKBENCH , new BlockWorkbench ( ) ) ; reg ( ENDER_CHEST , new BlockEnderchest ( ) ) ; reg ( CHEST , new BlockChest ( ) ) ; reg ( DISPENSER , new BlockDispenser ( ) ) ; reg ( DROPPER , new BlockDropper ( ) ) ; reg ( BOOKSHELF , new BlockDirectDrops ( Material . BOOK , 3 ) ) ; reg ( CLAY , new BlockDirectDrops ( Material . CLAY_BALL , 4 ) ) ; reg ( HARD_CLAY , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( STAINED_CLAY , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( WOODEN_DOOR , new BlockDoor ( Material . WOOD_DOOR ) ) ; reg ( IRON_DOOR_BLOCK , new BlockDoor ( Material . IRON_DOOR ) ) ; reg ( SPRUCE_DOOR , new BlockDoor ( Material . SPRUCE_DOOR_ITEM ) ) ; reg ( BIRCH_DOOR , new BlockDoor ( Material . BIRCH_DOOR_ITEM ) ) ; reg ( JUNGLE_DOOR , new BlockDoor ( Material . JUNGLE_DOOR_ITEM ) ) ; reg ( ACACIA_DOOR , new BlockDoor ( Material . ACACIA_DOOR_ITEM ) ) ; reg ( DARK_OAK_DOOR , new BlockDoor ( Material . DARK_OAK_DOOR_ITEM ) ) ; reg ( DOUBLE_STEP , new BlockDoubleSlab ( ) ) ; reg ( DOUBLE_STONE_SLAB2 , new BlockDoubleSlab ( ) ) ; reg ( WOOD_DOUBLE_STEP , new BlockDoubleSlab ( ) ) ; reg ( SOIL , new BlockDirectDrops ( Material . DIRT ) ) ; reg ( GLASS , new BlockDropless ( ) ) ; reg ( THIN_GLASS , new BlockDropless ( ) ) ; reg ( STAINED_GLASS , new BlockDropless ( ) ) ; reg ( STAINED_GLASS_PANE , new BlockDropless ( ) ) ; reg ( GLOWSTONE , new BlockRandomDrops ( Material . GLOWSTONE_DUST , 2 , 4 ) ) ; reg ( MYCEL , new BlockDirectDrops ( Material . DIRT ) ) ; <START_BUG> reg ( GRASS , new BlockDirectDrops ( Material . DIRT ) ) ; <END_BUG> reg ( DIRT , new BlockDirt ( ) ) ; reg ( GRAVEL , new BlockGravel ( ) ) ; reg ( SAND , new BlockFalling ( Material . SAND ) ) ; reg ( ANVIL , new BlockAnvil ( ) ) ; reg ( ICE , new BlockDropless ( ) ) ; reg ( PACKED_ICE , new BlockDropless ( ) ) ; reg ( SNOW , new BlockSnow ( ) ) ; reg ( SNOW_BLOCK , new BlockDropless ( ) ) ; reg ( PRISMARINE , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( RED_SANDSTONE , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( SANDSTONE , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( NETHER_BRICK , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( NETHER_FENCE , new BlockDirectDrops ( Material . NETHER_FENCE , ToolType . PICKAXE ) ) ; reg ( NETHERRACK , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( IRON_FENCE , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( BRICK , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( SMOOTH_BRICK , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( ENDER_STONE , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( COBBLESTONE , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( COBBLE_WALL , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( MOSSY_COBBLESTONE , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( STONE , new BlockStone ( ) ) ; reg ( OBSIDIAN , new BlockDirectDrops ( ToolType . DIAMOND_PICKAXE ) ) ; reg ( COAL_ORE , new BlockDirectDrops ( Material . COAL , ToolType . PICKAXE ) ) ; reg ( COAL_BLOCK , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( IRON_ORE , new BlockDirectDrops ( ToolType . STONE_PICKAXE ) ) ; reg ( IRON_BLOCK , new BlockDirectDrops ( ToolType . STONE_PICKAXE ) ) ; reg ( GOLD_ORE , new BlockDirectDrops ( ToolType . IRON_PICKAXE ) ) ; reg ( GOLD_BLOCK , new BlockDirectDrops ( ToolType . IRON_PICKAXE ) ) ; reg ( DIAMOND_ORE , new BlockDirectDrops ( Material . DIAMOND , ToolType . IRON_PICKAXE ) ) ; reg ( DIAMOND_BLOCK , new BlockDirectDrops ( ToolType . IRON_PICKAXE ) ) ; reg ( EMERALD_ORE , new BlockDirectDrops ( Material . EMERALD , ToolType . IRON_PICKAXE ) ) ; reg ( EMERALD_BLOCK , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( LAPIS_ORE , new BlockRandomDrops ( Material . INK_SACK , 4 , 4 , 8 , ToolType . STONE_PICKAXE ) ) ; reg ( LAPIS_BLOCK , new BlockDirectDrops ( ToolType . STONE_PICKAXE ) ) ; reg ( QUARTZ_ORE , new BlockDirectDrops ( Material . QUARTZ , ToolType . PICKAXE ) ) ; reg ( REDSTONE_ORE , new BlockRandomDrops ( Material . REDSTONE , 0 , 3 , 4 , ToolType . IRON_PICKAXE ) ) ; reg ( GLOWING_REDSTONE_ORE , new BlockRandomDrops ( Material . REDSTONE , 0 , 3 , 4 , ToolType . PICKAXE ) ) ; reg ( REDSTONE_BLOCK , new BlockDirectDrops ( ToolType . PICKAXE ) ) ; reg ( CARROT , new BlockCarrot ( ) ) ;

Fix:
reg ( GRASS , new BlockGrass ( ) ) ;